Book Review: 'Deep' by James Nestor

What kind of sport leaves competitors blacked out, with their skin blue and blood streaming from their mouths, noses and eyes?

By

Nancy Rommelmann

July 11, 2014 1:10 p.m. ET

Freediving is a sport where competitors plunge, sometimes lashed to weighted sleds, hundreds of feet below the ocean's surface without supplemental air. They hold their breath for as long as 11 minutes. But why would they want to? "Dozens, perhaps hundreds, of [free] divers are injured or die every year," notes the journalist James Nestor. Competing "seems like a death wish."

The freedivers that Mr. Nestor meets in "Deep: Freediving, Renegade Science, and What the Ocean Tells Us About...